1. Field of the Invention
The present invention relates to electronic components comprising a lead frame projecting from a side portion thereof, and more particularly to solid electrolytic capacitors.
2. Description of the Related Art
FIG. 7 is a perspective view showing a process for fabricating a solid electrolytic capacitor of the chip type, and FIG. 8 is a view in section taken along a plane containing the line A—A in FIG. 7 and showing the capacitor (see JP-B No. 3-30977).
With reference to FIG. 8, the solid electrolytic capacitor comprises a capacitor body 8 and a housing 7 made of a synthetic resin such as an epoxy resin or like thermosetting resin and covering the capacitor body. The capacitor has two lead frames 9, 90 electrically connected to the capacitor body 8 and projecting outward from respective opposite sides of the housing 7. The housing 7 comprises a lower half housing segment 71 and an upper half housing segment 70 provided on the segment 71. The lead frames 9, 90 are prepared from an alloy consisting mainly of iron and nickel.
The capacitor body 8 is fabricated in the following manner. An anode lead wire 2 is bonded or adhered to an anode body 1 which is a sintered body of valve metal, a dielectric oxide film 3 is formed on the anode body 1, and a cathode layer 4 of MnO2 (manganese dioxide) or a solid electrically conductive material of electrically conductive organic compound is formed on the film 3 to prepare a capacitor element 5 first as already known. The term “valve metal” refers to a metal forming a dielectric oxide film which is very compact and durable when subjected to an electrolytic oxidation treatment. Examples of such metals are Ti (titanium), Nb (niobium), etc. in addition to Al and Ta. Examples of electrically conductive organic compounds are electrically conductive high polymers such as polypyrrol, polythiophene, polyaniline and polyfuran, TCNQ (7,7,8,8-tetracyanoquinodimethane) complex salt, etc. Use of the conductive organic compound for the cathode layer 4 provides a capacitor of lower ESR (equivalent series resistance) and excellent high-frequency characteristics.
A carbon layer 6 is formed over the cathode layer 4 of the capacitor element 5, and a silver paste layer 60 is formed over the carbon layer 6 to provide the capacitor body 8.
The lead frame 9 is attached to the anode lead wire 2 as by resistance welding, and the other lead frame 90 is attached to the silver paste layer 60 with a silver adhesive.
Further as shown in FIG. 7, an upper die 45 and a lower die 46 providing a space corresponding to the housing 7 are prepared, and the capacitor body 8 having the lead frames 9, 90 attached thereto is place into the lower die 46. A resin is filled into the space between the two dies 45, 46, and the dies are thereafter removed to obtain a housing 7 having the lead frames 9, 90 projecting therefrom. The upper half housing segment 70 and the lower half housing segment 71 are each provided with tapered surfaces at opposite sides thereof so that the dies are smoothly removable. The butting faces of the two dies 45, 46 are indicated as P.L. (parting line) in FIG. 8.
Next, the lead frames 9, 90 are placed on a bending jig 75 as shown in FIG. 9. A force acting downward is applied to the outer end of each of the lead frames 9, 90 to bend the lead frame so as to provide a first piece 91 extending outward from the housing 7 and a second piece 92 extending downward from the outer end of the first piece 91.
The housing 7 is thereafter held at its midportion by a jig 55 as seen in FIG. 10. A roller 76 is pressed against each first piece 91 from thereabove to bend the first piece 91 downward about its base end portion.
Each second piece 92 is positioned in contact with the bottom of the housing 7 as shown in FIG. 8. Current is passed through the lead frames 9, 90 for aging to complete a capacitor. The second pieces 92, 92 are soldered to a mount board (not shown).
However, the conventional construction involves the likelihood that the bending force to be applied to the base end portion of the first piece 91 in bending the first piece 91 downward will be greater than is needed due to variations in the bending load to be applied, permitting a crack to develop in the base end portion. The crack produced in the lead frame 9 or 10 impairs the characteristics of the capacitor such as ESR.
An object of the present invention is to reduce the bending force to be applied to the base end portion to prevent cracking.